Neil Lennon said the failure of his much-changed Celtic team to beat Motherwell had given him "a lot to think about".
The champions were beaten 2-1 at Fir Park as Lennon, who must now prepare for a Scottish Cup quarter-final against St Mirren, paid for his decision to rest five players who started Saturday's rout of Dundee.
Georgios Samaras and Tomas Rogic were among those to get a chance from the start as top scorer Gary Hooper dropped to the bench, but a late Michael Higdon winner took the home side into second.
And after watching his side's lead at the top cut to a still-healthy 19 points, the manager said: "I'm raging. I made changes with games in mind but still put a strong team out.
"People keep coming to me looking to play - they got the opportunity and didn't play.
"It seems to me if I leave Hooper out the team then we suffer. We were very, very poor going forward in the first half."
Asked whether there was a lack of hunger among his players because they feel the SPL title is already won, Lennon said: "If that's the case they won't play here again. They can find another club and I'll play the kids.
"If they waste any game at this club and I detect that in their play, which was apparent in some cases, then it gives me a lot to think about. I'm pretty angry with some of the performances."
James Forrest escaped blame, Lennon saying: "I don't know how many decent balls James put into the box and there was no real desire to get on the end of things. The front line first half, apart from James, was insipid."